Process for the synthesis of mixtures of methane diphenyl diamine and its higher homologues with a controlled isomer distribution

ABSTRACT

A process for preparing methane diphenyl diamine (MDA) or a mixture of methane diphenyl diamine (MDA) and its higher homologues with a controlled isomer distribution using a modified zeolite having “shape selectivity”. The mixture contains compounds having the following general formula (I): where R represents a hydrogen atom or a C1 to C8 (iso)alkyl group, a C4 to C10 cycloalkyl group or a C6 to C12 aromatic group and n is a whole number greater than or equal to one so as to give a functionality of 2 to 6.

This invention relates to a process for preparing methane diphenyldiamine (MDA) or a mixture of methane diphenyl diamine (MDA) and itshigher homologues with a controlled isomer distribution. Morespecifically, this invention relates to a process for the preparation ofMDA or of mixtures of MDA and its higher homologues, in which the saidmixture contains compounds having the following general formula (I):

where R represents a hydrogen atom or a C1 to C8 (iso)alkyl group, a C4to C10 cycloalkyl group or a C6 to C12 aromatic group and n is a wholenumber greater than or equal to one so as to give a functionality of 2to 6, in which it is possible to control the concentration of dimericproducts, in particular of isomer 4.4′-MDA with respect to isomers2.4′-MDA and 2.2′-MDA.

Methane diphenyl diamine or the methane diphenyl diamine mixtures areused as intermediates in the preparation of the corresponding methanediphenyl diisocyanate (MDI), in turn used in the synthesis of a seriesof polymers for example polyurethanes, thermoplastic polymers and epoxyresins.

Methane diphenyl diamine may be produced from aniline or from one of itsderivatives by condensation with formaldehyde in the presence ofsolutions of strong acids, such as hydrochloric acid, sulphuric acid andphosphoric acid, as described, for example, in U.S. Pat. Nos. 2,683,730,3,277,173, 3,344,162; 3,362,979 or in H. Ulrich, “Chemistry andTechnology of Isocyanates” John Wiley and Sons, USA, 1996. The operatingconditions, necessary to produce a product with the specific structuralcharacteristics and without the formation of undesirable amounts ofby-products, typically requires the use of a sizable quantity of strongacid and consequently the use of large quantities of materials in theequipment which are capable of resisting such acids. Such constructionmaterials are often expensive. Further, after the MDA has beensynthesised, a corresponding amount of base material (typically sodiumhydroxide) is needed to neutralise the acid used, leading to theformation of sizable quantities of salts which may be contaminated byaromatic products and which need to be discharged. All theserequirements result in an increase in production costs.

Production processes based on using strong acid catalysts in which, forexample the synthesis is carried out in the presence of hydrophobicsolvents in order to totally or partially recycle the acid catalyst inan aqueous stage are known. These types of procedures introduce asolvent, which may be chlorinated and thus environmentallydisadvantageous, to the process and are described, for example, in U.S.Pat. No. 4,924,028 and U.S. Pat. No. 4,914,236.

To improve the process the use of other solvents (generally chlorinated)different from the initial substrate has been contemplated. Howeverchlorinated solvents may increase the risk of environmental damage.

U.S. Pat. No. 4,039,580 and U.S. Pat. No. 4,039,581 describe the use ofreusable solid acids, in particular clays, in the synthesis of MDA fromaniline and formaldehyde. In particular, the process in U.S. Pat. No.4,039,581 allows for the low temperature pre-condensation betweenaniline and formaldehyde and the elimination of water and methanol.Aminals are also obtained which come into contact with the solid acidcatalyst, at a temperature of between 20 and 55° C. to produce thecorresponding benzylamines. The benzylamines is then converted to theend products.

U.S. Pat. No. 4,071,558 describes a process using a solid acid catalystfor example Superfiltrol, in which the distribution of the dimericproducts is modulated, in particular of isomer 2.4′-MDA, based onselecting the operating conditions of condensation.

These are disadvantageous in that the acid catalysts generally requirevery low levels and suitably an absence of water in the aniline acetal.The water content is suitably not greater than 3% in weight, andpreferably less than 0.15% in weight, in order to avoid deactivation ofthe catalyst. Clays also present problems because they may be reused alimited number of times and, since their origin is natural and notsynthetic, consistent performance cannot be entirely reproduced dependson the particular batch.

The Applicants have now found a procedure for the preparation of MDA ina mixture with its higher homologues which allows distribution betweenthe main dimeric products to vary over a wide range and reduce or avoiddisadvantages with known processes. The ability to control the variationin the distribution allows a range of derivative products to be obtainedsuch as isocyanates, for example obtained by the phosgenation of MDA,with characteristic features. Further, the resulting MDA mixture isparticularly advantageous because MDA isomers are typically verydifficult to separate from each other. U.S. Pat. No. 4,034,039 disclosesa process in which separation of MDA isomers takes place throughsuccessive fractionated crystallization of MDA and phenol mixtures. Tobe able to control the isomer distribution enables a spectrum ofproducts having clearly different characteristics to be obtainedallowing products to be tailored for use in a variety of marketapplications.

The present invention is based on the surface modification of a zeolitecatalyst in acid form, described below, with an aqueous acidic solutioncomprising phosphoric acid and/or boric acid, “as is”, and, optionally,comprising a salt, for example an ammonium salt, thereof suitably, aftertreatment with an aqueous wash, solvent is removed and the catalystcalcined.

Without wishing to be bound by any theory, it is believed thatphosphoric acid and/or boric acid and the, if present their saltscombine with the zeolite's surface and, following a thermal treatmentstep give rise to species, believed to be polymer compounds which modifypore size and shape characteristics. “Catalysis on ZSM-5 zeolitesmodified by phosphorus” G. Oehlmann et al, Studies in Surface Scienceand Catalysis. Vol. 65, (1991), pages 1–20 illustrates methods by whichpore size and shape of zeolites may be modified.

Modifying the pore size and shape in a zeolite catalyst provides a meansof influencing catalyst selectivity (“shape selecting”).

Surprisingly, it was found that “shape selectivity” effects the ratiosof MDA isomeric distribution synthesized by means of acid catalysis,especially favouring the 4.4′-MDA isomer among the dimer products. Suchvariation of the isomer distribution may be modified and controlled bychanging the process with which phosphoric acid or boric acid iscombined with the zeolite. Furthermore, it has been found that zeolitein powder form and zeolite already in extruded form in the presence of abinder, for example, boehmite may be treated advantageously to provide“shape selecting”.

This invention provides a process for the preparation of MDA or amixture of MDA and its higher homologues having the general formula (I):

where R is independently selected from hydrogen, a C1 to C8 alkyl group,a C4 to C10 cycloalkyl group and a C6 to C12 aromatic group and n is awhole number greater than, or equal to one, suitably from 1 to 5 so asto give a functionality from 2 and 6, which comprises carrying out there-arrangement reaction of the intermediate having general formula (II):

in the presence of a zeolite in acid form with a “spaciousness index”from 2.5 to 19 modified on the surface by a process comprising i) one ormore treatments, for example impregnations, with an aqueous solutioncomprising phosphoric acid and/or boric acid, as is, and, optionally,comprising a salt, for example an ammonium salt thereof, ii) removal ofat least part of the solvent and iii) calcining the treated catalyst,preferably at a temperature of at least 400° and especially at least500° C.

Reference to “alkyl” herein shall be taken to include linear alkyl andbranched or “iso” alkyl groups unless otherwise stated.

The “spaciousness index” parameter measures the effective pore diameterof porous materials, such as zeolites. The “spaciousness index” is aparameter described in literature as, for example, in U.S. Pat. No.4,795,847 and in “Zeolites and Related Microporous Material: State ofthe Art 1994”, Studies in Surface Science and Catalysis, vol. 84, 37,1994, Elsevier Science B. V.; “Zeolite: Facts, Figures, Future”, 1989,1115, Elsevier Science Publishers, B. V.

According to the present invention, zeolites with a preferred“spaciousness index” of between 2.5 and 19 suitably are crystallinematerial having the composition (III):M^(n+) _(x/n)[(AlO₂)⁻ _(x)(SiO₂)].(H₂O)_(p)  [III]where x is less than 1, p is a whole number greater than or equal to 1,preferably from 1 to 20, M is a metal from Group IA or IIA, or is alanthanide, n is the valency of M, and where M may be partially ortotally exchanged for H⁺, (NH4)⁺, or (NR′4)⁺ where R′ is an alkyl group,for example C1 to C4 alkyl, or an aryl group.

Examples of zeolites which fall under the general formula (III) andwhich have a “spaciousness index” from 2.5 to 19 include beta zeolite,mordenite, ZSM-12, MCM-22 and ERB-1. Particular preference is given tobeta zeolite, for example as described in U.S. Pat. No. 3,308,069 with a“spaciousness index” of 19 and to zeolite ZSM-12.

Suitably the treatment of the zeolite is carried out by impregnation, inparticular by submerging solid particles of the zeolite in a liquidphase comprising phosphoric acid and/or boric acid, as is acid, as is,and, optionally, comprising a salt, for example an ammonium saltthereof, diluted in water at a concentration from 0.1 and 10% by weight.Suitably the treatment is carried out at a temperature of 20 to 100° C.At the end of this treatment, the liquid phase is removed, at least inpart, from the solid desirably by distillation under a vacuum. Suitablythe remaining solid is calcined, preferably at a temperature of 500 to600° C. The treatment may be repeated two or more times, for example 3to 5 times, with each treatment being followed by the correspondingremoval of liquid and calcination stage. The acid and optionally saltmay be the same or different in each treatment.

The zeolite used to prepare the catalyst employed in the presentinvention is suitably in acid form, that is, in the form in whichhydrogen ions occupy most of the cationic locations. In the surfacemodification treatment the zeolite may be used “as is” or may bemodified before the treatment by the partial isomorphic substitution ofaluminium by a metal selected from boron, iron and gallium. At the endof the treatment, the catalyst may be used “as is” or in combinationwith a binder, for example boehmite and alumina. The catalyst may beshaped in extruded tablets, for example as described in EP-A-847,802, orin any other suitable form. The surface tretment may be carried out onextruded tablets of the untreated zeolite if desired.

Suitably, the rearrangement reaction is carried out at a temperature of50 to 250° C., preferably from 120 to 200° C., in the presence of asolvent. Examples of suitable solvents include optionally substitutedaliphatic hydrocarbons, optionally substituted aromatic hydrocarbons,halogenated aromatic hydrocarbons and aniline. Examples of solventswhich are particularly suitable are aniline and aromatic chlorinatedhydrocarbons such as m-dichlorobenzene and chlorobenzene.

The intermediate in general formula (II) is a product referred to in theliterature, in particular when R is hydrogen. This intermediate may beobtained by condensing aniline, or derived from aniline in which R isdifferent from hydrogen, with formaldehyde, or a compound capable ofproducing formaldehyde under reaction conditions. In particular,formaldehyde may be used in an aqueous solution such as formaldehyde inan oligomerous state (for example trioxane and paraformaldehyde),dissolved in a solvent, suitably with aniline/formaldehyde molar ratiosof 2 to 10, preferably from 3 to 5. At the end of the synthesis, theintermediate in formula (II) is desirably separated by known methods,for example physical separation and distillation. The product thusobtained may contain water but the water content suitably is 3% or lessby weight and preferably 1.5% or less.

In a further aspect, the invention provides a process for thepreparation of methane diphenyl diamine in general formula (I) in whichthe rearrangement reaction may be carried out by contacting the zeolitecatalyst with a reaction mixture comprising aniline, or a derivative ofaniline, and formaldehyde, or a compound capable of producingformaldehyde under the reaction conditions. In this case, the aniline,or its derivative, is preferably present in stoichiometric excess andmay act as both a reagent and a solvent for the reaction at the sametime.

The rearrangement reaction may be carried out discontinuously,continuously or semi-continuously at ambient pressure or elevatedpressure such as to maintain the reactive system in a liquid state.

In a preferred embodiment, a procedure for the production of a compoundhaving general formula (I) comprises:

-   (a) reacting aniline, or a derivative of aniline and formaldehyde,    or a precursor of formaldehyde, so as to form an amine of    formula (II) optionally in a solvent, preferably aniline or its    derivative in the event that the aniline or its derivative is used    in sufficient excess;-   (b) removing water if present, from the amine (II) to a residual    concentration    -   of water of 3% or less, for example 1 to 3%, by weight of the        amine (II);-   (c) optionally diluting the product of step (b) in a solvent;-   (d) isomerising the amine (II) by feeding it into a reaction zone,    preferably one or more fixed bed reactors, containing a zeolite in    acid form with a “spaciousness index” of 2.5 to 19, modified on the    surface by a process comprising i) one or more treatments, for    example impregnations, with an aqueous solution comprising    phosphoric acid and/or boric acid, as is, and, optionally,    comprising a salt, for example an ammonium salt thereof, ii) removal    of at least part of the solvent and iii) calcining the treated    catalyst, preferably at a temperature of at least 400° and    especially at least 500° C., and wherein the reaction zone in    step d) is at an ambient pressure or such as to maintain the reagent    mixture in a liquid state and, preferably at a temperature of 50 to    250° C., more preferably 120 to 200° C.;-   (e) recovering the methane diphenyl diamine, and/or its higher    homologues, preferably by a purification process, for example,    distillation.

According to the present invention, the reagents in step (a) may be feddiscontinuously, continuously or semi-continuously to the reaction zone,suitably beginning with aniline and formaldehyde (or their derivativesor precursors). The pre-condensed material is subsequently fed into thereaction zone, preferably a fixed bed reactor, containing the treatedsolid acid catalyst, after water has been removed.

In step a), the reactants suitably are used in proportions from between2 to 15 moles of aniline or a derivative of it per mole of formaldehyde.Preferably the reaction in step (a) is carried out at a temperature ofbetween 10 to 60° C. and in the absence of an acid catalyst.

The pre-condensed amine (II) may be fed to the reaction zone bystaggering by using a vertical reactor fitted with two or more lateralinlets in a so-called split-feed.

Suitably, the separation of water from the amine (II) is carried out inaccordance with conventional techniques for example decanting anddistillation. The separation may be carried out at variable temperaturesor pressures according to the degree of residual water which it isdesired to have in the amine solution (II). Separating the water mayalso be carried out by using a combination of the techniques referredto, such as, for example, decanting followed by distillation.

At the end of the rearrangement reaction of the amine (II), thedistribution of the components in the composition of the mixtureobtained after isomerisation may subsequently be modified by totally orpartially recycling the mixture itself in the amine (II) synthesisreaction zone in step a) and/or in the rearrangement or isomerisationreaction zone.

A further process for the production of a compound having generalformula (I) comprises reacting aniline, or one of its derivatives, andformaldehyde, or one of its precursors, in one single reaction step,preferably in a complete mixing reactor, in the presence of a zeolite inacid form with a “spaciousness index” of 2.5 to 19 modified on thesurface by a process comprising i) one or more treatments, for exampleimpregnations, with an aqueous solution comprising phosphoric acidand/or boric acid, as is, and, optionally, comprising a salt, forexample an ammonium salt thereof, ii) removal of at least part of thesolvent and iii) calcining the treated catalyst, preferably at atemperature of at least 400° and especially at least 500° C., andremoving, preferably continually, for example by distilling, the waterof reaction or additional water with one or more reagents.

Suitably, the order of the single stage process is based on the use ofslurry reactors, either shaken or bubbled. Both the reagents, aniline(or one of its derivatives), and formaldehyde, (or one of itsprecursors), and the solid acid catalyst, optionally in the presence ofa solvent which preferably comprises excess aniline or its derivativeare fed, preferably simultaneously into a slurry reactor. Feeding of thereagents may be carried out continuously or by staggering the additionalong with one or more components of the reaction mixture.

The aniline/formaldehyde molar ratio used suitably is from 2 to 15, andpreferably from 3 to 5. Suitably the reaction temperature is from 50 to250° C. and preferably from 120 to 200° C. Suitably, the pressure isthat generated by the water with the reagents, or that which isgenerated during the reaction. Preferably the reaction mixture iscontinually agitated by an appropriate distillation system fitted to thereactor. The residence times in the liquid stage are suitably from 0.5to 10 hours and preferably from 1 to 8 hours.

In the event the catalyst is to be replaced, the catalyst suitably istotally replaced within a period of 5 hours to a period of 30 hours.Preferably, the catalyst/load weight ratio is between 1/20 and 1/300.

At the end of reaction, the catalyst suitably is filtered, and anyexcess aniline (and any residual water and/or solvent which may remain)are removed from the required product by conventional techniques, forexample by distillation.

The mixture of methane diphenyl diamine and/or its higher homologuessynthesised in accordance with the process described above may beconverted into the corresponding mixture of isocyanates in accordancewith the techniques referred to.

In order to understand the present invention better and to put it intopractice, there follow some examples which are for the purposes ofillustration and are not exhaustive.

EXAMPLE 1 Amine Synthesis (Reaction Intermediate)

The reaction intermediate in the formula:

is prepared by condensation between aniline and formaldehyde. Inparticular, an aqueous solution with 37% formaldehyde is fed, whilebeing stirred, into a reaction vessel containing aniline in order tohave a formaldehyde/aniline molar ratio equal to four: the temperatureis slowly raised to 50° C.

When the solution has been added, it is continued to be stirred for onehour, and then the organic stage consisting of amine and the anilinewhich has not reacted are then separated by a separator funnel. Theorganic stage is then dried to a maximum water content of 1.25% andretained for later use.

EXAMPLE 2 Zeolite Beta Synthesis

58.8 g of tetraethyl ammonium hydroxide in aqueous solution 40% byweight and 1.9 g of sodium aluminate (56% of Al₂O₃) are added to 58.4 gof demineralized water. It is heated to approximately 80° C. and it isleft under agitation until completely dissolved.

The clear solution thus obtained is added to 37.5 g of LUDOX HScolloidal silica with 40% by weight of SiO₂. An homogeneous solution isobtained, with a pH of 14, which is poured into a steel autoclave andleft to crystallize under hydrothermal conditions of 150° C. for 10days, under static conditions and autogenous pressure.

The crystallized product is separated by filtration, re-dispersed indemineralized water and filtered again. A damp zeolite cake is obtainedwhich contains the organic template tetraethylammonium and sodium.

EXAMPLE 3 Zeolite Beta Synthesis

The damp zeolite slab, prepared as described above in example 2 is driedin a oven for 1 hour at 150° C., calcined in a chamber furnace for 5hours at 550° C. in an air stream.

The calcined solids are dispersed in an aqueous solution of ammoniumacetate (150 g water and 8 g ammonium acetate) for the ion exchange.This suspension is heated under agitation for one hour approximately at80° C.

The suspension is then filtered and the obtained solids are re-dispersedin demineralized water (150 ml) to be washed. The suspension is thenfiltered and the ion exchange and the previous washing are repeated insequence. The solids are then washed again and dried in a oven for onehour at 150° C. thus obtaining zeolite in ammonic form. Said zeolite iscalcined in a chamber furnace for 5 hours at 550° C. in an air stream,obtaining zeolite beta (spaciousness index=19) in acid form.

An elementary chemical analysis shows the sodium residue in this zeoliteto be 106 ppm whereas the aluminum content is 3.14% ([Al]/[Na]=252).

The product is characterized through X ray diffraction from powders.

EXAMPLE 4 Zeolite Beta Synthesis

The moist cake obtained in Example 2 is redispersed an aqueous solutionof ammonium acetate (200 g of water and 16 g of ammonium acetate) forthe ion exchange. The suspension is heated under agitation for one hourat approximately 80° C.

The suspension is then filtered and the solids thus obtained arere-dispersed in 150 mL demineralized water to be washed. The suspensionis then filtered again and a moist zeolite cake in ammonic/alkyl ammonicform is thus obtained again.

An elementary chemical analysis shows the sodium residue in the lattersample to be 112 ppm. The aluminum content is 3.38% ([Al]/[Na]=257).

The product is characterized through X ray diffraction from powders.

EXAMPLE 5 Zeolite Beta Extrusion

A catalyst is prepared based on zeolite beta prepared according to thedescription in example 4, therefore not subject to calcination, and onalumina in the form of boehmite is. The catalyst has been extrudedaccording to the process described in example 4 EP 847 802.

EXAMPLE 6 Zeolite Beta Synthesis Treated with 5% (NH₄)₂HPO₄

5 g of zeolite beta are loaded into a glass balloon flask, preparedaccording to example 3, with molar ratio SiO₂/Al₂O₃=25, spaciousnessindex of 19, and 50 ml of a 5% (NH₄)₂HPO₄ solution in water.

The suspension is agitated at 90° C. for 1 hour, then the solvent isevaporated under vacuum.

The material thus obtained, in the form of a white powder, is calcinedin an stream of air at 550° C. for 5 hours. A calcined material devoidof carbon residue is obtained, the phosphorus content is shown to be10.14% (11.75% theoretical).

EXAMPLE 7 Zeolite Beta Synthesis Treated with (NH₄)₂HPO₄ at 2%

5 g of zeolite beta are loaded into a glass balloon flask, preparedaccording to example 3, with molar ratio SiO₂/Al₂O₃=25, spaciousnessindex of 19, and 50 ml of a 2% (NH₄)₂HPO₄ solution in water.

The suspension is agitated at 90° C. for 1 hour, then the solvent isvacuum evaporated.

The material thus obtained, in the form of a white power, is calcined inan stream of air at 550° C. for 5 hours. A calcined material devoid ofcarbon residue is obtained, the phosphorus content is found to be 4.59%(4.7% theoretical).

EXAMPLE 8 Zeolite Beta Synthesis Treated with 1% (NH₄)₂HPO₄

5 g of zeolite beta are loaded into a glass balloon flask, preparedaccording to example 3, with molar ratio SiO₂/Al₂O₃=25, spaciousnessindex of 19, and 50 ml of a 1% (NH₄)₂HPO₄ solution in water.

The suspension is agitated at 90° C. for 1 hour, then the solvent isvacuum evaporated.

The material thus obtained, in the form of a white power, is calcined inan stream of air at 550° C. for 5 hours. A calcined material free ofcarbon residue-is obtained, the phosphorus content is 2.30% (2.35%theoretical).

EXAMPLE 9 Zeolite Beta Synthesis Treated with 4% H₃BO₃

5 g of zeolite beta are loaded into a glass balloon flask, preparedaccording to example 3, with molar ratio SiO₂/Al₂O₃=25, spaciousnessindex of 19, and 50 ml of a 4% H₃BO₃ solution in water.

The suspension is agitated at 90° C. for 1 hour, then the solvent isvacuum evaporated.

The material thus obtained, in the form of a white power, is calcined inan air stream at 550° C. for 5 hours. A calcined material free of carbonresidue-is obtained, the boron content is found to be 6.6% (7%theoretical).

EXAMPLE 10 Zeolite Beta Synthesis Treated with H₃BO₃ at 2%

5 g of zeolite beta are loaded into a glass balloon flask, preparedaccording to example 3, with a molar ratio of SiO₂/Al₂O₃=25,spaciousness index of 19, and 50 ml of a 2% H₃BO₃ solution in water.

This suspension is agitated at 90° C. for 1 hour then the solvent isvacuum evaporated.

The material thus obtained, in the form of a white power, is calcined inan air stream at 550° C. for 5 hours. A calcined material devoid ofcarbon residue is obtained, with a boron content of 3.5% (3.5%theoretical).

EXAMPLE 11 Extruded Zeolite Beta Synthesis Treated with 2% (NH₄)₂HPO₄

5 g of zeolite beta are loaded into a glass balloon flask, previouslyextruded with 50% binder (boehmite) prepared according to example 4.Said zeolite, containing as active phase zeolite Beta with molar ratioSiO₂/Al₂O₃=25, spaciousness index of 19, is treated with 50 ml of a 2%(NH₄)₂HPO₄ solution in water.

The suspension is agitated at 90° C. for 1 hour, then the solvent isvacuum evaporated.

The material thus obtained, in the form of a white power, is calcined inan air stream at 550° C. for 5 hours. A calcined material devoid ofcarbon residues is obtained, the phosphorus content is found to be 4.79%(4.7% theoretical).

EXAMPLE 12 Extruded Zeolite Beta Synthesis Treated with H₃BO₃ at 4%

5 g of previously extruded zeolite beta prepared according to example 4with 50% binder (boehmite) are loaded into a glass round bottomflask.Said zeolite, containing as active phase zeolite Beta with molar ratioSiO₂/Al₂O₃=25, spaciousness index of 19, is treated with 50 ml of a 4%H₃BO₃ solution in water.

The suspension is agitated at 90° C. for 1 hour, then the solvent isvacuum evaporated.

The material thus obtained, in the form of a white power, is calcined inan air stream at 550° C. for 5 hours. A calcined material devoid ofcarbon residues is obtained, with a boron content of 6.8% (7%theoretical).

EXAMPLE 13 Zeolite ZSM-12 Synthesis Treated with 2% (NH₄)₂HPO₄

5 g of zeolite ZSM-12 in acid form, prepared as described in U.S. Pat.No. 3,832,449, with molar ratio SiO₂/Al₂O₃=102, spaciousness index 3,and 50 ml of a 2% (NH₄)₂HPO₄ solution in water are loaded into a roundbottom flask.

The suspension is agitated at 90° C. for 1 hour, then the solvent isvacuum evaporated.

The material thus obtained, in the form of a white power, is calcined inan air stream at 550° C. for 5 hours. A calcined material devoid ofcarbon residues is obtained, with a boron content of 3.69% (4.7%theoretical).

EXAMPLE 14 Zeolite ZSM-12 Synthesis Treated with H₃BO₃ at 2%

5 g of zeolite ZSM-12 in acid form, with molar ratio SiO₂/Al₂O₃=102,spaciousness index of 3, and 50 ml of H₃BO₃ in a 2% solution in waterare loaded into a glass balloon flask.

The suspension is agitated at 90° C. for 1 hour, then the solvent isvacuum evaporated.

The material thus obtained, in the form of a white power, is calcined inan air stream at 550° C. for 5 hours A calcined material devoid ofcarbon residues is obtained, with a boron content of 3.4% (3.5%theoretical).

EXAMPLE 15 (COMPARATIVE) Catalytic Test with Untreated Zeolite Beta

4 g of amminal, 10 g of aniline and 125 mg of zeolite beta preparedaccording to example 3, with molar ratio SiO₂/Al₂O₃=25 are loaded in aglass autoclave.

The autoclave is closed and kept under agitation for 6 hours at 150° C.

Finally, the mass is cooled to ambient temperature and the reactionsolvent is removed through distillation at reduced pressure.

The reaction product is analyzed by HPLC using the analysis methoddescribed in Journal für Praktische Chemie, Band 328, Heft 1, 1986,142–148.

-   Conversion: 100%;-   selectivity to 4.4′-MDA: 54,99%;-   selectivity to 2.4′+2.2′-MDA: 24,67%;-   molar ratio 4.4′/(2.4′+2.2′): 2,2-   trimers: 11,95%;-   heavy components: 10,13%.

EXAMPLE 16 Batch Catalytic Test with Zeolite Beta Treated with(NH₄)₂HPO₄ at 5%

4 g of amminal, 10 g of aniline and 1 g of zeolite beta in acid formtreated with (NH₄)₂HPO₄ at 5%, prepared according to example 6 areloaded in a glass autoclave. The autoclave is closed and kept underagitation for 6 hours at 150° C.

Finally, the mass is cooled to ambient temperature and the reactionsolvent is separated through distillation at reduced pressure.

The reaction product is analyzed by HPLC using the analysis methoddescribed in Journal für Praktische Chemie, Band 328, Heft 1, 1986,142–148.

-   Conversion: 100%;-   selectivity to 4.4′-MDA: 69.59-   selectivity to 2.4′-MDA: 11.63%;-   selectivity to 2.2′-MDA: 0%-   molar ratio 4.4′/(2.4′+2.2′): 5.98-   trimers and heavy components: 18.76%;

EXAMPLE 17 Batch Catalytic Test with Zeolite Beta Treated with(NH₄)₂HPO₄ at 2%

4 g of amminal, 10 g of aniline and 125 mg of zeolite beta in acid formtreated with (NH₄)₂HPO₄ at 2%, prepared according to example 7 areloaded in a glass autoclave. The autoclave is closed and kept underagitation for 6 hours at 150° C.

Finally, the mass is cooled to ambient temperature and the reactionsolvent is separated through distillation at reduced pressure.

The reaction product is analyzed by HPLC using the analysis methoddescribed in Journal für Praktische Chemie, Band 328, Heft 1, 1986,142–148.

-   Conversion: 100%;-   selectivity to 4.4′-MDA: 69.41-   selectivity to 2.4′-MDA: 18.70%;-   selectivity to 2.2′-MDA: 0%-   molar ratio 4.4′/(2.4′+2.2′): 3.71-   trimers and heavy components: 11.88%;

EXAMPLE 18 Batch Catalytic Test with Zeolite Beta Treated with(NH₄)₂HPO₄ al 1%

4 g of amminal, 10 g of aniline and 125 mg of zeolite beta in acid formtreated with (NH₄)₂HPO₄ at 1%, prepared according to example 8 areloaded in a glass autoclave. The autoclave is closed and kept underagitation for 6 hours at 150° C.

Finally, the mass is cooled to ambient temperature and the reactionsolvent is separated through distillation at reduced pressure.

The reaction product is analyzed by HPLC using the analysis methoddescribed in Journal für Praktische Chemie, Band 328, Heft 1, 1986,142–148.

-   Conversion: 100%;-   selectivity to 4.4′-MDA: 65.60-   selectivity to 2.4′-MDA: 20.43%;-   selectivity to 2.2′-MDA: 2.61%-   molar ratio 4.4′/(2.4′+2.2′): 2.85-   trimers and heavy components: 11.36%;

EXAMPLE 19 Catalytic Test in Batch with Extruded Zeolite Beta Treatedwith (NH₄)₂HPO₄ at 2%

4 g of amminal, 10 g of aniline and 125 mg of extruded zeolite beta inacid form treated with (NH₄)₂HPO₄ at 2%, prepared according to example11 are loaded in a glass autoclave. The autoclave is closed and keptunder agitation for 6 hours at 150° C.

Finally, the mass is cooled to ambient temperature and the reactionsolvent is separated through distillation at reduced pressure.

The reaction product is analyzed by HPLC using the analysis methoddescribed in Journal für Praktische Chemie, Band 328, Heft 1, 1986,142–148.

-   Conversion: 100%;-   selectivity to 4.4′-MDA: 69.1%-   selectivity to 2.4′-MDA: 21.19%;-   selectivity to 2.2′-MDA: 4.36%-   molar ratio 4.4′/(2.4′+2.2′): 2.70-   trimers and heavy components: 5.34%;

EXAMPLE 20 Batch Catalytic Test with Zeolite Beta Treated with H₃BO₃ al4%

4 g of amminal, 10 g of aniline and 1 g of zeolite beta in acid formtreated with H₃BO₃ at 4%, prepared according to example 9, are loaded ina glass autoclave. The autoclave is closed and kept under agitation for6 hours at 150° C.

Finally, the mass is cooled to ambient temperature and the reactionsolvent is separated through distillation at reduced pressure.

The reaction product is analyzed by HPLC using the analysis methoddescribed in Journal für Praktische Chemie, Band 328, Heft 1, 1986,142–148.

-   Conversion: 100%;-   selectivity to 4.4′-MDA: 67.57-   selectivity to 2.4′-MDA: 9.73%;-   selectivity to 2.2′-MDA: 0%-   molar ratio 4.4′/(2.4′+2.2′): 6.94-   trimers and heavy components: 22.68%;

EXAMPLE 21 Batch Catalytic Test with Zeolite Beta Treated with H₃BO₃ at2%

4 g of amminal, 10 g of aniline and 125 mg of zeolite beta in acid formtreated with H₃BO₃ at 2% are loaded in a glass autoclave, as shown inexample 10. The autoclave is closed and kept under agitation for 6 hoursat 150° C.

Finally, the mass is cooled to ambient temperature and the reactionsolvent is separated through distillation at reduced pressure.

The reaction product is analyzed by HPLC using the analysis methoddescribed in Journal für Praktische Chemie, Band 328, Heft 1, 1986,142–148.

-   Conversion: 100%;-   selectivity to 4.4′-MDA: 73.04-   selectivity to 2.4′-MDA: 14.54%;-   selectivity to 2.2′-MDA: 0%-   molar ratio 4.4′/(2.4′+2.2′): 5.02-   trimers and heavy components: 12.41%;

EXAMPLE 22 Batch Catalytic Test with Extruded Zeolite Beta Treated withH₃BO₃ al 4%

4 g of amminal, 10 g of aniline and 1 g of extruded zeolite beta in acidform treated with H₃BO₃ at 4% are loaded in a glass autoclave, as inexample 12. The autoclave is closed and kept under agitation for 6 hoursat 150°.

Finally, the mass is cooled to ambient temperature and the reactionsolvent is separated through distillation at reduced pressure.

The reaction product is analyzed by HPLC using the analysis methoddescribed in Journal für Praktische Chemie, Band 328, Heft 1, 1986,142–148.

-   Conversion: 100%;-   selectivity to 4.4′-MDA: 67.59%-   selectivity to 2.4′-MDA: 15.49%;-   selectivity to 2.2′-MDA: 3.21%-   molar ratio 4.4′/(2.4′+2.2′): 3.63-   trimers and heavy components: 13.7%;

EXAMPLE 23 (COMPARATIVE) Catalytic Test with Untreated ZSM-12 Zeolite

4 g of amminal, 10 g of aniline and 1 g of extruded ZSM 12 zeolite inacid form with molar ratio SiO₂/Al₂O₃=102 are loaded in a glassautoclave.

The autoclave is closed and kept under agitation for 6 hours at 150° C.Finally, the mass is cooled to ambient temperature and the reactionsolvent is separated through distillation at reduced pressure.

The reaction product is analyzed by HPLC using the analysis methoddescribed in Journal für Praktische Chemie, Band 328, Heft 1, 1986,142–148.

-   Conversion: 100%;-   selectivity to 4.4′-MDA: 54.50%;-   selectivity to 2.4′+2.2′-MDA: 30.36%-   molar ratio 4.4′/(2.4′+2.2′): 1.66-   trimers: 10.76%;-   heavy components: 2.87%.

EXAMPLE 24 Catalytic Test with ZSM 12 Treated with (NH₄)₂HPO₄ at 2%

4 g of amminal, 10 g of aniline and 19 of ZSM 12 zeolite in acid formtreated with (NH₄)₂HPO₄ at 2%, as in example 13 are loaded in a glassautoclave.

The autoclave is closed and kept under agitation for 6 hours at 150° C.

Finally, the mass is cooled to ambient temperature and the reactionsolvent is separated through distillation at reduced pressure.

The reaction product is analyzed by HPLC using the analysis methoddescribed in Journal für Praktische Chemie, Band 328, Heft 1,1986,142–148.

-   Conversion: 100%;-   selectivity to 4.4′-MDA: 64.86%-   selectivity to 2.4′-MDA: 11.85%;-   selectivity to 2.2′-MDA: 0.%-   molar ratio 4.4′/(2.4′+2.2′): 5.47-   trimers and heavy components: 23.29%;

EXAMPLE 25 Catalytic Test with ZSM 12 Treated with H₃BO₃ at 2%

4 g of amminal, 10 g of aniline and 1 g of zeolite ZSM 12 in acid formtreated with H₃BO₃ at 2% are loaded in a glass autoclave, as shown inexample 14. The autoclave is closed and kept under agitation for 6 hoursat 150° C.

Finally, the mass is cooled to ambient temperature and the reactionsolvent is separated through distillation at reduced pressure.

The reaction product is analyzed by HPLC using the analysis methoddescribed in Journal für Praktische Chemie, Band 328, Heft 1, 1986,142–148.

-   Conversion: 100%;-   selectivity to 4.4′-MDA: 66.40%-   selectivity to 2.4′-MDA: 11.20%;-   selectivity to 2.2′-MDA: 2.95%-   molar ratio 4.4′/(2.4′+2.2′): 4.69-   trimers and heavy components: 19.62.%;

EXAMPLE 26 Catalytic Test in a Fixed Bed Reactor with Untreated ZeoliteBeta

(Comparative)

5 cm³ of zeolite beta prepared according to example N. 3, with molarratio SiO₂/Al₂O₃=25, compressed at 20 ton and sifted at 70–100 mesh areloaded in a tubular reactor with a diameter of 12.5 mm and length of 390mm. A mixture of 30% amminal by volume in aniline, is then fed into thereactor at a temperature of 180° C., at 4 bar pressure and an L.H.S.V.(Liquid Hourly Space Velocity) of 7.2 h⁻¹, referred to the active phase.

Samples are taken at the times indicated in table 1 which, followingsolvent separation at reduced pressure, are analyzed according to thepreviously described method.

For all samples the amminal conversion is total.

TABLE 1 Time on Ratio Heavy stream 4.4′/(2.4′ + 2.4′ + components +(t.on.s.) (h) 2.2′) 4.4′ MDA % 2.2′ MDA % Trimers % 2 2.06 63.40 30.795.81 4 2.13 64.04 30.06 5.36 6 2.08 63.77 30.56 5.67 20  2.08 64.0130.72 5.27 24  2.14 64.31 30.07 5.62

EXAMPLE 27 Catalytic Test in Fixed Bed Reactor with Zeolite Beta Treatedwith (NH₄)₂HPO₄ at 1%

5 cm³ of zeolite beta, treated with (NH₄)₂HPO₄ at 1% (prepared accordingto example 8), compressed at 20 ton and sifted with 70–100 mesh areloaded in a tubular reactor with a diameter of 12,5 mm and length 390mm. A mixture of 30% amminal by volume in aniline is then fed into thereactor, at a temperature of 180° C., at 4 bar pressure and an L.H.S.V.(Liquid Hourly Space Velocity) of 7.2 h⁻¹, referred to the active phase.

Samples are taken at the times indicated in table 2 which, followingsolvent separation at reduced pressure, are analyzed according to thepreviously described method.

For all samples amminal conversion is total.

TABLE 2 Heavy t.on.s. Ratio 2.4′ + 2.2′ components + (h) 4.4′/(2.4′ +2.2′) 4.4′ MDA % MDA % Trimers %  2 2.48 66.72 26.83 6.45  4 2.52 65.2625.9 8.84 18 2.53 63.49 25.09 11.42 20 2.54 62.79 24.72 12.49 22 2.5262.04 24.6 13.33 24 2.60 60.35 23.2 16.44

1. A process for the preparation of methane diphenyl diamine or amixture of methane diphenyl diamine and its higher homologues having thegeneral formula (I):

where R is independently selected from hydrogen, a C1 to C8 alkyl group,a C4 to C10 cycloalkyl group or a C6 to C12 aromatic group and n is awhole number from 1 to 5 so as to give a functionality from 2 and 6,which comprises carrying out the re-arrangement reaction of theintermediate having general formula (II):

in the presence of a zeolite in acid form with a “spaciousness index”from 2.5 to 19 modified on the surface by a process comprising i) one ormore treatments with an aqueous solution comprising phosphoric acidand/or boric acid, as is, and, optionally, comprising a salt thereof,ii) removal of at least part of the solvent and iii) calcining thetreated catalyst.
 2. A process according to claim 1, in which thezeolite comprises a synthetic crystalline material having thecomposition (III):M^(n+) _(x/n)[(AlO₂)⁻ _(x)(SiO₂)].(H₂O)_(p)  [III] where x is less than1, p is a whole number greater than or equal to 1, M is a metal fromGroups IA or IIA, or is a lanthanide, n is the valency of M, and where Mmay be partially or totally exchanged for H⁺, (NH4)⁺, or for(NR′4)⁺where R′ is an alkyl group or an aryl group. aliphatichydrocarbons, optionally substituted aromatic hydrocarbons, halogenatedaromatic hydrocarbons and aniline.
 3. A process according to claim 2, inwhich the zeolite is selected from beta zeolite, mordenite, ZSM-12,MCM-22 and ERB-1.
 4. A process according to claim 3, in which thezeolite is selected from beta zeolite and ZSM-12.
 5. A process accordingto claim 1 in which the surface modification treatment is carried out bysubmerging zeolite solid particles in a liquid phase comprisingphosphoric acid and/or boric acid, as is and, optionally, comprising asalt thereof, diluted in water at a concentration of 0.1 and 10% byweight and at a temperature ranging between 20 and 100° C.
 6. A processaccording to claim 1 in which, at the end of the treatment in step i) tomodify the zeolite, at least part of the liquid phase is removed and theremaining solids are calcined a temperature of at least 400° C.
 7. Aprocess according to claim 1 in which the surface modification treatmentis repeated one or more times.
 8. A process according to claim 1 inwhich the zeolite is modified as is or after the partial isomorphicsubstitution of aluminium by a metal selected from boron, iron andgallium.
 9. A process according to claim 1 in which the surface-modifiedzeolite is in the form of extruded tablets and the modification isperformed directly on the extruded tablets.
 10. A process according toclaim 1 in which the zeolite is mixed with a binder.
 11. A processaccording to claim 1 in which the rearrangement reaction is carried outat a temperature of 50 to 250° C.
 12. A process according to claim 1 inwhich the rearrangement reaction takes place in the presence of asolvent, selected from optionally substituted aliphatic hydrocarbons,optionally substituted aromatic hydrocarbons, halogenated aromatichydrocarbons and aniline.
 13. A process according to claim 12, in whichthe solvent is selected from aniline and a chlorinated aromatic solvent.14. A process according to claim 1 in which the intermediate containswater in a quantity equal to or less than 3% by weight.
 15. A processfor the preparation of methane diphenyl diamine of general formula (I),

where R is independently selected from hydrogen, a C1 to C8 alkyl group,a C4 to C10 cycloalkyl group and a C6 to C12 aromatic group and n is awhole number from 1 to 5 so as to give a functionality from 2 and 6, inwhich a rearrangement reaction is carried out by contacting a zeolite inacid form with a “spaciousness index” from 2.5 to 19 modified on thesurface by a process comprising i) one or more treatments with anaqueous solution comprising phosphoric acid and/or boric acid, as is,and, optionally, comprising a salt thereof, ii) removal of at least partof the solvent and iii) calcining the treated catalyst, with a reactionmixture comprising aniline, or a derivative of aniline, andformaldehyde, or a compound capable of producing formaldehyde under thereaction conditions.
 16. A process according to claim 15, in which thereaction is carried out with an excess of aniline, or its derivative,which acts as a reagent and a solvent.
 17. A process for the productionof a compound having general formula (I)

wherein R is independently selected from hydrogen, a C1 to C8 alkylgroup, a C4 to C1 cycloalkyl group and a C6 to C12 aromatic group and nis a whole number from 1 to 5 so as to give a functionality from 2 and6, comprising: (a) reacting aniline, or a derivative of aniline, andformaldehyde, or a precursor of formaldehyde, so as to form an amine,optionally in the presence of a solvent; (b) removing water if present,from the reaction product of (a) to a residual concentration of water of3% or less by weight of the amine; (c) optionally diluting the productof step (b) in a solvent; (d) isomerising the amine by feeding it into areaction zone containing a zeolite in acid form with a “spaciousnessindex” of 2.5 to 19, modified on the surface by a process comprising i)one or more treatments with an aqueous solution comprising phosphoricacid and/or boric acid, as is, and, optionally, comprising a saltthereof, ii) removal of at least part of the solvent and iii) calciningthe treated catalyst, and wherein the reaction zone in step d) is at anambient pressure or such as to maintain the reagent mixture in a liquidstate at a temperature of 50 to 250° C.; and (e) recovering the methanediphenyl diamine, and/or its higher homologues.
 18. A process accordingto claim 17, in which the amine (II) is fed to the reaction zone in adiscontinuous manner using a vertical reactor fitted with two or morelateral inlets.
 19. A process according to claim 17 in which the mixtureobtained after isomerisation is totally or partially recycled in step a)or in step d).
 20. A process for the production of a compound havinggeneral formula (I)

where R is independently selected from hydrogen, a C1 to C8 alkyl group,a C4 to C10 cycloalkyl group and a C6 to C12 aromatic group and n is awhole number greater than, or equal to one, suitably from 1 to 5 so asto give a functionality from 2 and 6, which comprises reacting aniline,or one of its derivatives, and formaldehyde, or one of its precursors,in a single reaction step in the presence of a zeolite in acid form witha “spaciousness index” of 2.5 to 19 modified on the surface by a processcomprising i) one or more treatments with an aqueous solution comprisingphosphoric acid and/or boric acid, as is, and, optionally, comprising asalt thereof, ii) removal of at least part of the solvent and iii)calcining the treated catalyst.
 21. A process according to claim 20, inwhich the aniline/formaldehyde molar ratio is from 2 to 15, the reactiontemperature is from 50 to 250° C. and the pressure is such that thewater added with the reagents, or formed during the reaction, iscontinuously removed from the reaction step.
 22. A process according toclaim 20 in which times in the liquid phase range between 0.5 and 10hours and the catalyst/load weight ratio ranges between 1/20 and 1/300.